Generally, a cutting insert is fastened to a cutting tool mounted on a machine tool and used for cutting a workpiece that is generally formed of ferrous or nonferrous metals, non-metal material, and so on.
An example of such cutting insert is disclosed in Korean Registration Patent No. 10-0949660.
Referring to FIGS. 1 to 3, a related cutting insert will be described. For reference, FIGS. 1 to 3 each correspond to FIGS. 1, 4 and 8 of KR10-00949660, and the same reference numerals are used for convenience of explanation. Further, the same names of the elements are used as used in KR10-00949660.
The related cutting insert is a double-sided cutting insert 10 for use with a milling cutter, in which outer peripheral surface 14 is extended between two opposed end surfaces 12 and includes two identical minor-side surfaces generally in a shape of parallelogram, two opposed identical major-side surfaces 18, and corner-side surface positioned between adjacent minor- and major-side surfaces 16, 18.
Meanwhile, the related cutting insert adopts double-sided type, and a side surface 18 is formed basically in a negative shape, so that it is difficult to provide more than a certain level of cutting performance. That is, as illustrated in FIG. 3, enhancement of cutting performance is limited, as there is limit to achieving a large axial rake angle of the major cutting edge 34.
Further, as illustrated in FIGS. 2 and 3, since the thickness of the insert (transversal thickness of the insert with reference to FIG. 2) is considerably increased, the number of inserts applicable for use with the milling cutter with the same machining diameter is limited and the machining productivity is limited.
Further, as seen in FIGS. 1 and 3, the entire minor-side surface 16 is formed as a negative surface. Accordingly, there is a problem in that, when the insert is set to ensure a sufficient clearance angle, the axial rake angle of the major cutting edge 34 decreases and the cutting performance is deteriorated.
Specifically, the related double-sided cutting insert uses a portion (i.e., inner end surface 46) of the end surfaces 12 (upper and lower surfaces) as a mounting surface, and uses the other as an inclined surface (i.e., rake surface 44) to discharge chips (see paragraphs [0044] and [0047] of KR10-00949660 for reference). Accordingly, the surface area of the mounting surface for mounting with the milling cutter body is narrow, and considerable problem occurs (e.g., breakage of the fastening screw passed through the cutting insert and fastened into the milling cutter body during high-speed high-stiffness machining, or generation of vibration during cutting process, or the like).
Further, when set in the cutter body such that the upper surface is used as the rake surface, the lower surface is used as the mounting surface. Alternatively, when the lower surface is used as the rake surface, the upper surface is used as the mounting surface. This relationship causes problem such as deteriorated performance due to limits to designing of rake surface for chip evacuation, designing of helix angles, and so on. Meanwhile, in an example of a flat-shaped insert in which a side surface is formed as a positive surface, since the side surface serving as the mounting surface is formed as a positive surface, constraining force is decreased after fastening with the cutter body, and problem of vibration occurs due to cutting impact during cutting process.